Good evening,
I am trying to understand in which cases the sequence would be used, for the example below, since the rowids would not always give me a single row to manage the changes.
Why consider a sequence of additional fields?
I will be grateful if you could clarify the doubt, with some example.
Thank you so much,
Greetings.
CREATE MATERIALIZED VIEW LOG ON sales
WITH ROWID, SEQUENCE(amount_sold, time_id, prod_id)
INCLUDING NEW VALUES;
Now imagine that you want to create a materialized view that contains aggregates on this table. Because the materialized view log has been created with all referenced columns in the materialized view's defining query, the materialized view is fast refreshable. If DML is applied against the sales table, then the changes are reflected in the materialized view when the commit is issued.
CREATE MATERIALIZED VIEW sum_sales
REFRESH FAST ON COMMIT AS
SELECT s.time_id, COUNT(*) AS count_grp,
SUM(s.amount_sold) AS sum_dollar_sales,
COUNT(s.amount_sold) AS count_dollar_sales
FROM sales s
GROUP BY s.time_id;
Without using the sequence, you will have the following error
ORA-12033: cannot use filter columns from materialized view log on "ADMIN"."SALES"
So let me try to explain why, by using a Testcase
drop table sales;
create table sales (time_id number, prod_id number, amount_sold number)
CREATE MATERIALIZED VIEW LOG ON sales
WITH ROWID, SEQUENCE(amount_sold, time_id, prod_id)
INCLUDING NEW VALUES;
truncate table sales;
insert into sales values (1,1,23);
insert into sales values (1,2,23);
commit;
select time_id, sum(amount_sold) from sales group by time_id;
TIME_ID SUM(AMOUNT_SOLD)
------- ----------------
1 46
Now Imagine, that you will modify a row multiple times.
update sales set amount_sold = 55 where time_id = 1 and PROD_ID = 1;
update sales set amount_sold = 12 where time_id = 1 and PROD_ID = 1;
select time_id, sum(amount_sold) from sales group by time_id;
TIME_ID SUM(AMOUNT_SOLD)
------- ----------------
1 35
your new amount_sold is 35. How to do a fast refresh without reading the value for the row (1,2) because you only modified (1,1)
select * from MLOG$_SALES where DMLTYPE$$ != 'I' order by ;
AMOUNT_SOLD TIME_ID PROD_ID M_ROW$$ SEQUENCE$$ SNAPTIME$$ DMLTYPE$$ OLD_NEW$$ CHANGE_VECTOR$$ XID$$
----------- ------- ------- ------------------ ---------- -------------------- --------- --------- --------------- ----------------
23 1 1 AAAwaSAAAAAAFpTAAA 105 4000-01-01T00:00:00Z U U CA== 4222223434942993
55 1 1 AAAwaSAAAAAAFpTAAA 106 4000-01-01T00:00:00Z U N CA== 4222223434942993
55 1 1 AAAwaSAAAAAAFpTAAA 107 4000-01-01T00:00:00Z U U CA== 4222223434942993
12 1 1 AAAwaSAAAAAAFpTAAA 108 4000-01-01T00:00:00Z U N CA== 4222223434942993
So you can use the previous value 46 and increment/decrement using the old/new value as follow
select 46 - 23 + 55 - 55 + 12 as newval from dual;
NEWVAL
------
35
You can also do the same when doing a delete
This is not possible having only the rowid. To generate the new value 35 you need to read an unmodified value, so you cannot do a fast refresh.
Hope that this can help you to understand in which cases the sequence is used
Related
I am looking for a possibly better approach to this.
I have created a temp table in Oracle 11.2 that I'm using to pre calculate values that I will need in other selects instead of always generating them again with each select.
create global temporary table temp_foo (
DT timestamp(6), --only the date part will be used in this example but for later things I will need the time
Something varchar2(100),
Customer varchar2(100),
MinDate timestamp(6),
MaxDate timestamp(6),
Filecount int,
Errorcount int,
AvgFilecount int,
constraint PK_foo primary key (DT, Customer)
) on commit preserve rows;
I then first insert some fixed values for everything except AvgFilecount. AvgFilecount should contain the average for the Filecount for the 3 previous records (going by the date in DT). It doesn’t matter that the result will be converted to an int, I don’t need the decimal places
DT | Customer | Filecount | AvgFilecount
2019-04-30 | x | 10 | avg(2+3+9)
2019-04-29 | x | 2 | based on values before this
2019-04-28 | x | 3 | based on values before this
2019-04-27 | x | 9 | based on values before this
I thought about using a normal UPDATE statement as this should be faster than looping through the values. I should mention that there are no gaps in the DT field but obviously there is a first one where I won‘t find any previous records. If I would loop through, I could easily calculate AvgFilecount with (the record before previous record/2 + previous record)/3 which I cannot with UPDATE as I cannot guarantee the order of how they are executed. So I‘m fine with just taking the last 3 records (going by DT) and calcuting it from there.
What I thought would be an easy update is giving me headaches. I‘m mostly doing SQL Server where I would just join the 3 other records but it seems is a bit different in Oracle. I have found https://stackoverflow.com/a/2446834/4040068 and wanted to use the second approach in the answer.
update
(select curr.DT, curr.temp_foo, curr.Filecount, curr.AvgFilecount as OLD, (coalesce(Minus1.Filecount, 0) + coalesce(Minus2.Filecount, 0) + coalesce(Minus3.Filecount, 0)) / 3 as NEW
from temp_foo curr
left join temp_foo Minus1 ON Minus1.Customer = curr.Customer and trunc(Minus1.DT) = trunc(curr.DT-1)
left join temp_foo Minus2 ON Minus2.Customer = curr.Customer and trunc(Minus2.DT) = trunc(curr.DT-2)
left join temp_foo Minus3 ON Minus3.Customer = curr.Customer and trunc(Minus3.DT) = curr.DT-3
order by 1, 2
)
set OLD = NEW;
Which gives me an
ORA-01779: cannot modify a column which maps to a non key-preserved
table
01779. 00000 - "cannot modify a column which maps to a non key-preserved table"
*Cause: An attempt was made to insert or update columns of a join view which
map to a non-key-preserved table.
*Action: Modify the underlying base tables directly.
I thought this should work as both join conditions are in the primary key and thus unique. I am currently implementing the first approach in the above mentioned answer but it is getting quite big and it feels like there should be a better solution to this.
Other things I thought about trying:
using a nested subselect (nested because Oracle doesn’t know top(n) and I need to sort the subselect) to select the previous 3 records ordered by DT and then he outer select with rownum <=3 and then I could just use AVG(). However, I was told subselect can be quite slow and joins are better in Oracle performance wise. Dunno if that is really the case, haven‘t done any testing
Edit: My insert right now looks like this. I am already aggregating the Filecount for a day as there can be multiple records per DT per Customer per Something.
insert into temp_foo (DT, Something, Customer, Filecount)
select dates.DT, tbl1.Something, tbl1.Customer, coalesce(sum(tbl3.Filecount),0)
from table(Function_Returning_Daterange(NULL, NULL)) dates
cross join
(SELECT Something,
Code,
Value
FROM Table2 tbl2
WHERE (Something = 'Value')) tbl1
left outer join Table3 tbl3
on tbl3.Customer = tbl1.Customer
and trunc(tbl3.MinDate) = trunc(dates.DT)
group by dates.DT, tbl1.Something, tbl1.Customer;
You could use an analytic average with a window clause:
select dt, customer, filecount,
avg(filecount) over (partition by customer order by dt
rows between 3 preceding and 1 preceding) as avgfilecount
from tmp_foo
order by dt desc;
DT CUSTOMER FILECOUNT AVGFILECOUNT
---------- -------- ---------- ------------
2019-04-30 x 10 4.66666667
2019-04-29 x 2 6
2019-04-28 x 3 9
2019-04-27 x 9
and then do the update part with a merge statement:
merge into tmp_foo t
using (
select dt, customer,
avg(filecount) over (partition by customer order by dt
rows between 3 preceding and 1 preceding) as avgfilecount
from tmp_foo
) s
on (s.dt = t.dt and s.customer = t.customer)
when matched then update set t.avgfilecount = s.avgfilecount;
4 rows merged.
select dt, customer, filecount, avgfilecount
from tmp_foo
order by dt desc;
DT CUSTOMER FILECOUNT AVGFILECOUNT
---------- -------- ---------- ------------
2019-04-30 x 10 4.66666667
2019-04-29 x 2 6
2019-04-28 x 3 9
2019-04-27 x 9
You haven't shown your original insert statement; it might be possible to add the analytic calculation to that, and avoid the separate update step.
Also, if you want the first two date values to be calculated as if the 'missing' extra days before them had zero counts, you could use sum and division instead of avg:
select dt, customer, filecount,
sum(filecount) over (partition by customer order by dt
rows between 3 preceding and 1 preceding)/3 as avgfilecount
from tmp_foo
order by dt desc;
DT CUSTOMER FILECOUNT AVGFILECOUNT
---------- -------- ---------- ------------
2019-04-30 x 10 4.66666667
2019-04-29 x 2 4
2019-04-28 x 3 3
2019-04-27 x 9
It depends what you expect those last calculated values to be.
dataSource:
username type rank
a 106 1
a 116 2
a 126 3
b 106 1
b 106 2
when remove a,116,2 this record return:
username type rank
a 106 1
a 126 2
b 106 1
b 106 2
when insert a,116 return:
username type rank
a 106 1
a 126 2
a 116 3
b 106 1
b 106 2
I choose use tigger to realize:
insert(succeed):
create or replace trigger bi_auto
before insert
on auto
for each row
declare
-- local variables here
begin
select count(rank)+1 into :new.rank from auto where username=:new.username;
end bi_auto;
delete(fail,return ora-04091, ora-06512, ora-04088):
create or replace trigger bd_auto
after delete
on auto
for each row
declare
-- local variables here
begin
insert into session_auto
select username, type, rank() over(partition by username order by rank) ranknew from auto where username=:old.username order by username;
delete from auto where username=:old.username;
insert into auto select * from session_auto;
end bd_auto;
Please help me to modify it,thanks.I know there is something wrong with the performance, but I want to know how to realize.
I think the entire approach is problematic and error prone. It would be much easier to calculate the rank dynamically. If you want the convenience of querying a table, you could just add it to a view:
CREATE OR REPLACE VIEW auto_view AS
SELECT username, type, RANK() OVER (PARTITION BY username ORDER BY TYPE ASC) r
FROM auto
If performance is that big of an issue, you could always materialize your view.
I have two tables affiliation and customer, in that i have data like this
aff_id From_cus_id
------ -----------
1 10
2 20
3 30
4 40
5 50
cust_id cust_aff_id
------- -------
10
20
30
40
50
i need to update data for cust_aff_id column from affiliation table which is aff_id like below
cust_id cust_aff_id
------- -------
10 1
20 2
30 3
40 4
50 5
could u please give reply if anyone knows......
Oracle doesn't have an UPDATE with join syntax, but you can use a subquery instead:
UPDATE customer
SET customer.cust_aff_id =
(SELECT aff_id FROM affiliation WHERE From_cus_id = customer.cust_id)
merge into customer t2
using affiliation t1 on (t1.From_cus_id =t2.cust_id )
WHEN MATCHED THEN
update set t2.cust_aff_id = t1.aff_id
;
Here is an update with join syntax. This, quite reasonably, works only if from_cus_id is primary key in the first table and cust_id is foreign key in the second table, referencing the first table. Without these conditions, the requirement doesn't make much sense in the first place anyway... but Oracle requires that these constraints be stated explicitly in the tables. This is also reasonable on Oracle's part IMO.
update
( select t1.aff_id, t2.cust_aff_id
from affiliation t1 join customer t2 on t2.cust_id = t1.from_cus_id) j
set j.cust_aff_id = j.aff_id;
I am currently doing some testing and am in the need for a large amount of data (around 1 million rows)
I am using the following table:
CREATE TABLE OrderTable(
OrderID INTEGER NOT NULL,
StaffID INTEGER,
TotalOrderValue DECIMAL (8,2)
CustomerID INTEGER);
ALTER TABLE OrderTable ADD CONSTRAINT OrderID_PK PRIMARY KEY (OrderID)
CREATE SEQUENCE seq_OrderTable
MINVALUE 1
START WITH 1
INCREMENT BY 1
CACHE 10000;
and want to randomly insert 1000000 rows into it with the following rules:
OrderID needs to be be sequential (1, 2, 3 etc...)
StaffID needs to be a random number between 1 and 1000
CustomerID needs to be a random number between 1 and 10000
TotalOrderValue needs to be a random decimal value between 0.00 and 9999.99
Is this even possible to do? I can I could generate all of these using this update statement? however generating a million rows in 1 go I am not sure on how to do this
Thanks for any help on this matter
This is how i would randomly generate the number on update:
UPDATE StaffTable SET DepartmentID = DBMS_RANDOM.value(low => 1, high => 5);
For testing purposes I created the table and populated it in one shot, with this query:
CREATE TABLE OrderTable(OrderID, StaffID, CustomerID, TotalOrderValue)
as (select level, ceil(dbms_random.value(0, 1000)),
ceil(dbms_random.value(0,10000)),
round(dbms_random.value(0,10000),2)
from dual
connect by level <= 1000000)
/
A few notes - it is better to use NUMBER as data type, NUMBER(8,2) is the format for decimal. It is much more efficient for populating this kind of table to use the "hierarchical query without PRIOR" trick (the "connect by level <= ..." trick) to get the order ID's.
If your table is created already, insert into OrderTable (select level...) (same subquery as in my code) should work just as well. You may be better off adding the PK constraint only after you create the data though, so as not to slow things down.
A small sample from the table created (total time to create the table on my cheap laptop - 1,000,000 rows - was 7.6 seconds):
SQL> select * from OrderTable where orderid between 500020 and 500030;
ORDERID STAFFID CUSTOMERID TOTALORDERVALUE
---------- ---------- ---------- ---------------
500020 666 879 6068.63
500021 189 6444 1323.82
500022 533 2609 1847.21
500023 409 895 207.88
500024 80 2125 1314.13
500025 247 3772 5081.62
500026 922 9523 1160.38
500027 818 5197 5009.02
500028 393 6870 5067.81
500029 358 4063 858.44
500030 316 8134 3479.47
I have two tables BASE and DAILY as shown below:
BASE
Cust ID IP address
1 10.5.5.5
2 10.5.5.50
3 10.5.5.6
DAILY
Cust ID IP address
1 10.5.5.5
2 10.5.5.70
4 10.5.5.67
The table DAILY is periodically refreshed every 24 hours. Now for every Cust Id in BASE I have to check if the IP address is modified in DAILY. If yes then update the row in BASE.
All the new entries in DAILY have to be inserted into BASE.
I have tried this using a Cursor comparing and then updating and then another cursor for insertion.
But it is taking lot of time.
What is the best possible way to do this?
You could also use MERGE depending on your database system.
SQL Server syntax would be
MERGE INTO BASE B
USING DAILY D
ON D.CustId = B.CustId
WHEN NOT MATCHED THEN
INSERT (CustId, Ip) VALUES (D.CustId, D.Ip)
WHEN MATCHED AND D.Ip <> B.Ip THEN
UPDATE SET B.Ip = D.Ip;
Oracle PL/SQL syntax seems to be much the same, take a look here
If you just want to update all your BASE table, use an UPDATE to update all the rows in your BASE table.
UPDATE `BASE`
SET `IP address` = (SELECT `IP address`
FROM DAILY
WHERE DAILY.`Cust ID` = `BASE`.`Cust ID`);
Then, use this INSERT INTO query to insert new values that not exists in your table BASE.
INSERT INTO `BASE`
SELECT `Cust ID`, `IP address`
FROM DAILY
WHERE DAILY.`Cust ID` NOT IN (SELECT `Cust ID` FROM BASE);
SQL>
declare
begin
for i in (select * from daily where ip_add not in (select ip_add from base))
loop
update base set ip_add=i.ip_add where custid=i.custid;
end loop;
end;
PL/SQL procedure successfully completed.
SQL> select * from base;
CUSTID IP_ADD
---------- ----------
1 10..5.5.5
2 10..5.5.20 -- updated value from base where ip_add is different
3 10..5.5.6
SQL> select * from base ;
CUSTID IP_ADD
---------- ----------
1 10..5.5.5
2 10..5.5.20
4 10..5.5.62
SQL>